Hormone Concentrations and Semen Parameters in Criollo Breed Stallions Under Training.

The study examines the potential impact of physical training on the reproductive efficiency of Criollo breed stallions, specifically focusing on hormone concentrations and semen parameters. The results indicate that while hormones such as testosterone and estradiol remained unaffected, cortisol levels rose post-training, and various semen parameters were affected negatively.

Research Objective and Methodology

• The study aimed to examine the potential reduction in reproductive efficiency in Criollo stallions due to the stress associated with training. It compared the semen quality and hormone concentrations under two conditions; 1) stallions undergoing regular training and competitive events and 2) stallions undergoing regular field conditions without any training or competitive participation.
• A total of 18 Criollo breed stallions were used for the experiment, nine of which were part of the exercise group and the remaining nine were the control group. The exercise group performed an hour of training per day and participated in competitions during the experimental period.
• Serum and semen samples were acquired from the stallions every fifteen days, with a gap of an hour between two ejaculates. The researchers evaluated sperm mobility, velocity, and morphology with the help of a phase-contrast microscope and determined concentration via a hemocytometer.
• Several staining methods and survival tests were used to analyze the sperm cells in both raw and diluted samples. The hormonal levels of cortisol, testosterone, and estradiol were measured using radioimmunoassay.

Key Findings

• The results revealed that testosterone and estradiol concentrations remained unaffected by the exercise (P = .28 and P = .97, respectively). However, cortisol concentration was found to increase after the training regimen in the exercise group.
• Several semen parameters were found to be influenced by the exercise regimen. The parameters that showed significant changes due to the exercise included gel-free volume, sperm motility, total number of sperm, normal sperm morphology, and total number of morphologically normal and motile sperm.
• The exercise did not influence certain semen parameters such as color, pH, and sperm concentration.
• Although training exerted a negative impact on seminal quality, important to note is that all affected semen parameters remained within the normal range for equines.

Relevance of the Research

• This research provides a broader understanding of the potential impact of physical stressors such as training on the reproductive efficiency of the Criollo breed stallions. It suggests that while training does not notably affect testosterone and estradiol concentrations, it leads to an increase in cortisol levels and affects numerous seminal parameters negatively.
• The results may have important implications for managing the training and breeding programs for Criollo and potentially other breeds, with the aim to maintain optimal reproductive efficiency.